Printing control circuits have been developed but these have shortcomings which affect their usefulness as regard accurate and consistent printing of characters. These devices have employed a light comb arrangement to determine the position of the printed output. In the case of a matrix type character print-out a synchronized pulsed light beam together with a fixed comb-like member having a plurality of apertures is utilized together with a photodetector on the print head to determine the actual position of said print head. Such output positional information is then utilized to control the speed of said print head in order to achieve consistent character printing. Magnetic output detection means have also been utilized to determine the actual position of the print head.